This invention relates to the invention described and claimed in co-pending application Ser. No. 562,309 filed Dec. 16, 1983, and which is hereby incorporated by reference in its entirety.
The invention herein is incorporated into an assembly for collecting a liquid sample from a patient, such as a blood sample. More particularly, this invention relates to a needle assembly for collecting single and multiple liquid samples from such a patient with the use of the single assembly herein. The device utilizes a housing chamber for the samples with walls which are translucent or transparent, for visually indicating whether or not proper access to the sample source in question has been achieved.
Moreover, a material which is highly absorbent to aqueous containing solutions is utilized in the form of a substantially cylindrical sleeve providing air passage so that gas displaced by a liquid sample moving into the housing chamber may be vented, followed by an immediate swelling of the material upon exposure of the liquid sample to prevent any discharge of the liquid sample from the housing chamber. The sleeve is comprised of a solid compacted material which is of a size allowing an air bleed passage between the walls of the sleeve and the adjacent walls of the housing containing the sleeve. The material swells on contact with the liquid closing the bleed passage or passages.
As taught in the above-referenced co-pending application, the tablet forming the cylindrical sleeve seals the chamber against discharge of the sample, while simultaneously providing for the venting of gas displaced by that same sample. Once entry has been made to the source of the liquid sample, as indicated by the transparent or translucent chamber walls visually showing the presence of the sample in the housing chamber, then multiple samples may be collected from the housing chamber by being drawn sequentially into a plurality of vacuum collection devices. The assembly incorporates a separate flexible self-sealing elastomeric sleeve which cooperates with the discharge opening of the device during periods of exchange of the vacuum collection devices for sequential discharge of additional samples.
In certain instances, it has been found that when the compacted tablet sleeve embodiment described in co-pending application Ser. No. 562,309 is used, due to radial clearances present in the assembly, it is possible for the tablet to move to one side, presenting a much larger opening to flow than if clearances were concentric. This may be caused simply by gravity. At any rate, this causes a momentary uneven response to the initial quantity of blood, and has the effect of a slight delay in blocking blood flow during the initial vein entry indication procedures for taking a blood sample.
With this invention by contrast, the tablet cylinder or sleeve is mounted on a tapered hub post. The taper is such that the hub post diameter increases toward the negative pressure end of the device. This causes a wedging action which holds the tablet sleeve axis concentric to the cooperating hub axis to form a device which reacts evenly around its entire circumference to the sample. Because of this, there is an even response in the form of initial venting of air pockets in the assembly when vein entry has been achieved through the sleeve, followed rapidly and almost simultaneously by a swelling of the compacted sleeve material to block blood flow before an evacuated sample receiving tube is attached to the negative cannula end of the assembly. Thus, at the moment when the blood comes into contact with the sleeve, the sleeve expands evenly and concentrically around its supporting hub by absorbing the aqueous content of the blood sample, and preventing any further movement past the sleeve.
As discussed above, it is desirable to provide a mechanism whereby the user of such a needle assembly can be informed when the intravenous needle has penetrated the source of the sample to be obtained, such as the vein of the patient for collection of a blood sample. Many times in collecting blood from a patient, it is difficult to locate the vein, or for other reasons blood flow into the collecting device is not adequate. In those instances, it is advantageous to be able to make a quick determination that entry into the vein has been made, and that blood is flowing into the needle assembly. Once this determination has been made and the vein entry achieved, the evacuated blood collection containers can be inserted into the collection assembly in accordance with well known techniques of collecting blood samples during a collection procedure involving a single vein entry.
The invention here is arranged to overcome one of the problems which arises during the venipuncture step in that pockets of air are present in the various needle assemblies. When veni-puncture is made, and the evacuated blood collection container is not yet attached to the opposite end of the structure, blood cannot flow into the needle assembly because of a pocket of air which, under normal atmospheric conditions, remains inside the needle assembly. Thus, even though vein entry may have been accomplished, blood flow may not begin, simply because of the air pocket blockage in the assembly.
Both U.S. Pat. Nos. 4,207,870 and 4,398,544, assign to the common assignee herewith, utilize a porous plug in blood collection assemblies of the kind described herein. Both of these arrangements utilize a material which is air pervious and liquid impervious. The material is a sintered material which is occluded by the movement of a blood sample into the interstices of the porous material. Both patents describe inventions utilizing relatively complicated valve structures, including movable internal parts. Although the inventions recognize the utilization of a porous material for providing a venting for displaced air during receiving a blood sample, there is still room for improvement over such a device. That is, absolute positive sealing may not always be achieved merely by physical occlusion, although generally such procedures are effective.
By contrast, in the present invention, the material is in the form of a separate sleeve or tablet which may be inserted in a mechanical manner between the two parts forming a housing during the construction thereof in a production line. The arrangement herein is a simplified structure comprising a highly absorbent material in the form of a cylinder, which swells in contact with aqueous substances. The material is of the highly absorbent material compressed from that material into a sleevelike cylindrical tablet form, which is inserted mechanically between the two parts forming the housing. As will be understood by practitioners-in-the-art of constructing multiple blood collection assemblies, these cylinders may be formed separately in large numbers for insertion in a mass production line between the two parts forming the housing, with all such procedures being handled by robots.
Before describing this invention in more detail, it may be well to note that the material forming the substantially cylindrical vent sleeve of the invention may be comprised of a hydrolyzed starch-polyacrylonitrile graft copolymer with side chains containing carboxamide and carboxylate groups, such as WATER-LOCK A100, WATER-LOCK A125, ducts of Grain Processing Corporation, 1600 Oregon Street, Muscatine, Iowa 52761. Other sources include Henkel Corporation, 4620 West 77th Street, Minneapolis, Minn., Super Absorbent Company, Route 3, P.O. Box 342, Lumberton, N.C. and Edison Hydrocontrol Chemicals Inc., 99 Madison Avenue, New York, N.Y. 10016.
The absorbent polymeric compositions of the invention may be prepared by the procedures taught in U.S. Pat. Nos. 4,045,387; 4,134,863; 3,981,100; 4,159,260; 3,661,815; 3,935,099 and 3,985,616.
Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings and the appended claims.